Conventional electrical junction boxes are four inches square (i.e., four inches on a side) and two and one-eighth inches deep. In approximately 1978, fire alarm signaling units of the type including a strobe light and either an audio speaker or chimes, sometimes called speaker-strobe or chime-strobe alarm signaling units, were introduced. Conventional junction boxes were inadequate in size to accommodate the alarm signaling units (or similar devices) and the electrical conductors necessary to power the signaling units. Accordingly, the industry began to use an extension ring in combination with a conventional junction box, as shown in FIG. 1.
The extended junction box assembly 70 includes a conventional four inch by four inch by two and one-eighth inch deep junction box 71 having a four inch by four inch by one and one-half inch extension ring 72 connected thereto with screws 73 (one shown). The forward end of the extension ring 72 is provided with a pair of diagonally-opposed flanges or mounting brackets 74 for mounting a device such as an alarm signaling unit thereto (not shown). However, this extended four-inch square combination unit has been found to have a few disadvantages. In particular, the available volume inside the extended junction box assembly 70 is still often inadequate to contain both the alarm signaling unit and various electrical conductors that must be accommodated in the box for powering the particular alarm signaling unit and related components (e.g., other alarm signaling units and/or other electrical devices down the line).
The extension ring 72 depth is limited to one and one-half inches because the combined depth of a conventional four square junction box 71 and a one and one-half inch deep extension ring 72 is the maximum that will approximately fit in a three and one-half inch conventional stud space when mounted on a bar hanger. In fact, the combined depth of about three and three-quarters inches may cause a small but undesirable bow on the back side of the wall when mounted on a bar hanger. Furthermore, as shown in FIG. 1, the inner flange or ridge 75 that facilitates joining the junction box 71 and the extension ring 72, can interfere with the conductors and terminal strip of the device as they are installed in the assembly.
To mitigate these problems, a second generation electrical junction box and adapter ring assembly was developed, as disclosed in U.S. Pat. No. 6,103,972, the disclosure of which is hereby expressly incorporated by reference. Referring to FIG. 2, the second generation junction box 10 defines a cavity 12 that is designed to receive the speaker portion 14 or other protruding structure of an alarm signaling unit 18, such as a speaker-strobe signaling unit. An adapter or an extension ring 16 provides an interface between the junction box 10 and the alarm signaling unit 18.
The junction box 10 includes a rear wall 20 and four forwardly-extending sidewall panels 22, 24, 26, and 28. In order to accommodate both the speaker portion 14 of the alarm signaling unit 18 and associated electrical wires and connections, and still fit within the space typically provided between a wall (e.g., sheetrock) and an interior bar hanger on which the assembly will typically be mounted, the improved junction box 10 measures approximately five inches square and two and seven-eighths inches deep. The rear wall 20 of the junction box 10 includes a number of conventional knock-outs 30, as do the sidewalls 22, 24, 26, and 28, for receiving the ends of conductor-carrying conduits (not shown) and connectors (not shown).
The extension ring 16 includes a substantially square peripheral flange 44, each side of which is approximately five inches in length and one-half inch wide, so as to define an approximately four inch square opening 47 for receiving the speaker portion 14 of the signaling unit 18. Screw slots 46 and 48 are provided in the flange 44 and are positioned so that at least two of the slots will align with screw holes in two of four mounting brackets 50 provided on the front edges of two sidewalls 22 and 26 of the junction box 10. An approximately four inch square flange or wall 52 extends forwardly from the flange 44. Mounting brackets 54 are provided in two diagonally opposite corners so as to align with two of the mounting screw holes 42 in the conventional alarm signaling unit 18.
To assemble the second generation junction box 10 and extension ring 16 to the signaling unit 18, the extension ring 16 is first mounted on the junction box 10 via screws 56 which extend through slots 46 or 48 in the flange 44 of the extension ring 16 and through the holes in mounting brackets 50 on the front five inch square peripheral edge of the junction box 10. The alarm signaling unit 18 is mounted to the extension ring 16 with screws 58 extending through two diagonally-opposed mounting holes 42 in the front grill panel 60 of the alarm signaling unit 18 and into the aligned holes of two diagonally-opposed, aligned mounting brackets 54 of the extension ring 16, wherein the speaker portion 14 extends into the cavity 12 in the junction box 10. As the screws 58 are tightened, a sealing surface 59 of the signaling unit 18 is pressed against a mounting surface 61, such as an interior wall. As so assembled, the enlarged area in the cavity 12 of the junction box 10 will accommodate the speaker portion 14 and a relatively large number of conductors (not shown), some of which will attach to the speaker portion 14, and others of which will then pass through the junction box 10 and on to the next alarm signaling unit (or other electrical device) down the line, thereby avoiding the need for multiple junction boxes.
Although this second generation junction box 10 and extension ring 16 are effective for dry and/or interior applications, there remains a need for a junction box assembly that provides a semi-flush or flush mounted, weather-resistant exterior installation of alarms and the like. It was found that when the signaling unit 18 is mounted to a mounting surface 61 through the use of two diagonally opposed mounting brackets 54, as shown in FIG. 2, it is difficult to achieve a weather-resistant seal between the sealing surface 59 and the mounting surface 61. The diagonal connections do not provide a uniform force about the perimeter of the signaling unit 18, and may cause the signaling unit 18 to distort slightly, diminishing the ability of the sealing surface 59 to form a contaminate- and weather-resistant seal upon the mounting surface 61. Thus, water and other contaminates may infiltrate the signaling unit 18 and electrical components contained within the junction box 10. Contaminate infiltration may provide a safety hazard, as it may cause electrical shorts resulting in a fire or may cause the signaling unit to become inoperative, in addition to causing costly component damage.
In many prior art installations a weather-resistant seal is provided by using a specifically designed box adapted to receive the signaling unit (or similar device). Such boxes are designed to mount directly to an exterior surface of a building. A disadvantage to these prior art boxes is that they protrude relatively far from the wall, and they require the conduit coupled to the junction box to be run along an exterior surface of the wall. Such exterior mounted conduit is unsightly and susceptible to impact damage.
Similarly, there is a need for an extension ring compatible for use with alarm signaling units 18 having only a single mounting aperture. For example, the extension ring 16 pictured in FIG. 2 is incompatible with certain alarm signaling units of the type having a single, centrally located mounting aperture.
Accordingly, it is an object of the present invention to provide an electrical junction box extension ring which will permit the convenient and contaminate resistant mounting of an alarm signaling unit upon a mounting surface.
Another object of the present invention is to provide an electrical junction box extension ring, which permits the mounting of a signaling unit having a single mounting aperture to an electrical junction box.